1. Field of the Invention
The invention is in the field of reactive atomization and spray deposition of metal matrix composites, and in particular, relates to the control of a combination of reactive and nonreactive alloys with refinements to synthesize materials containing in-situ dispersoids.
2. Description of the Prior Art
Roberts et al., "Techniques for Producing Fine Metal Powder," U.S. Pat. No. 5,147,448 (1992), is directed to a gas atomization process for forming metal powder. Roberts discusses reactive atomization wherein the reactive phases of the material are more coarse and ductile so that they string out when deformed and act as a fiber reinforcement.
Watson et al., "Copper Alloys with Dispersed Metal Nitrides and Method of Manufacture," U.S. Pat. No. 5,102,620 (1992), describes a process using a reactive element, which is soluble in the metal alloy, reacts with the atomization atmosphere during the deposition process and provides a deposited metal matrix in which reinforcing particles are incorporated. The process is described as spray casting in a reactive atmosphere.
Werner et al., "Method and Device for Manufacturing a Powder of Amorphous Ceramic or Metallic Particles," U.S. Pat. No. 4,966,737 (1990), Kelley, "Method for Producing Closed Cell Spherical Porosity and Spray Formed Metals," U.S. Pat. No. 5,266,099 (1993); Ashok et al., Spray Cast Copper Composites," U.S. Pat. No. 5,390,722 (1995); and Gilman et al., "Magnesium Based Metal Matrix Composites Produced from Rapidly Solidified Alloys," U.S. Pat. No. 5,273,569 (1993), show systems for codeposition of materials. Kelley is directed to codeposition of metallic elements with blowing agents such as barium carbonate. Ashok describes spray casting composites wherein the first constituent may be a reactive element, and the second constituent another metal or reinforcing element such as carbon fiber. Gilman describes a composite material produced from a base metal matrix and a reinforcing phase. A dispersion of a reinforcing phase into the magnesium matrix of Gilman is described as being performed by atomization techniques.
Chun et al., "Production of Charged Uniformly Sized Metal Droplets," U.S. Pat. No. 5,266,098 (1993) and Orme et al., "Method and Apparatus for Droplet Stream Manufacturing," U.S. Pat. No. 5,226,948 (1993), both describe metal droplet deposition methods. Chun suggests utilizing a pulse gas jet oscillating at a predetermined frequency in order to provide a narrow distribution of the metal droplets in a manner compared to conventional gas atomization techniques. Orme discloses modulation of the metal droplet generators to provide a predetermined spray variation.
Dietrich et al., "CVD Process for the Production of a Superconducting Fiber Bundle," U.S. Pat. No. 4,657,776 (1987); Brill et al., "Multilayer Web for Reducing Loss of Radiant Heat," U.S. Pat. No. 4,532,181 (1985); Miura et al., "Method of Making Composite Material of Matrix Metal and Fine Metallic Particles Dispersed Therein," U.S. Pat. No. 4,626,410 (1986); Klesse et al., "Thin-Film Resistor and Process for the Production Thereof," U.S. Pat. No. 4,204,935 (1980), each describe a deposition process or composite material formation process utilizing a reactive atomization technique. Dietrich for example, describes a plasma activated chemical vapor deposition process which discloses deposition of a superconducting material on a fiber reinforcement.
Feest et al., "Metal Matrix Composite Manufacture," U.S. Pat. No. 4,928,745 (1990); Watson et al., "Substrate for Spray Cast Strip," U.S. Pat. No. 5,240,061 (1993); Leatham et al., "Spray Deposition Method and Apparatus Thereof," U.S. Pat. No. 5,143,139 (1992); and Eadie, "Method and Apparatus for Producing Strip Products by a Spray Forming Technique," U.S. Pat. No. 5,393,321 (1995), show deposition processes utilizing atomization. Although none of these references are specifically directed to reactive atomization, Leatham discloses the addition of particulates to form a composite coating which was disclosed in a copending published foreign application. Feest describes codeposition of reinforcing material particulates in the context of an atomization process. Uebber et al., "Process and Apparatus for Producing Rotationally Symmetrical Bodies," U.S. Pat. No. 5,297,613 (1994).
Anderson et al., "Method of Making Environmentally Stable Reactive Alloy Powders," U.S. Pat. No. 5,372,629 (1994); Anderson et al., "Gas Atomization Synthesis of Refractory of Intermetallic Compounds and Supersaturated Solid Solutions," U.S. Pat. No. 5,368,657 (1994); Biancaniello et al., "Producing Void-Free Metal Alloy Powders by Melting as well as Atomization Under Nitrogen Ambient," U.S. Pat. No. 5,114,470 (1992); Ashdown et al., "Fine Hollow Particles of Metals and Metal Alloys and Their Production," U.S. Pat. No. 5,024,695 (1991); Anderson et al., Environmentally Stable Metal Powders," U.S. Pat. No. 5,073,409 (1991); Choudhury, "Process for Producing Superconductive Ceramics by Atomization of Alloy Precursor Under Reactive Atmospheres or Post Annealing Under Oxygen," U.S. Pat. No. 4,985,400 (1991), each describe reactive atomization processes. Each of these references discusses the formation of a powder composition utilizing reactive atomization.
O'Handley et al., "Bulk Rapidly Solidified Magnetic Materials," U.S. Pat. No. 5,225,004 (1993), is directed generally to a system for producing powder material utilizing an atomization process, although is not necessarily a reactive atomization process. Liquid dynamic compaction is a process of direct fabrication of solid, even massive, bodies directly from a molten spray of fine, atomized liquid or semiliquid droplets. The process combines the advantages of rapid solidification with simultaneous consolidation to a final shape directly from the rapid quenched droplets while providing exposure only to the chosen atmosphere or gas used in the atomization process itself, typically, helium and argon. E. J. Lavernia, "Liquid Dynamic Compaction of a Rapidly Solidified 7075 Aluminum Alloy Modified with 1 Percent Nickel and 0.8 percent zirconium," MS Thesis 1984, MIT, Cambridge, Mass.
In the liquid dynamic compaction process during gas atomization, a stream of molten alloy is broken or shattered into a spray of fine droplets by jets of high velocity inert gas. The droplets solidify rapidly due to their large surface areas and high velocity relative to the atomizing gas and are collected in a cyclone collector at the bottom of an atomizing chamber with the particles ranging in size from a few microns to a few hundred microns. Essentially all the droplets are completely liquid and have not started to crystallize when they contact a metallic substrate surface placed beneath the atomization cone. A powder is used in the process or used in combination with inert gas such as argon or helium in a chamber and for atomization. Therefore, during the process, the pressure in the spray deposition chamber is slightly positive, for example, about 1 psig. Difficulties in dealing with reactive alloys, such as fine powders of aluminum and rare earth containing alloys, can be accommodated in practice by using an inert gas filled spray deposition chamber. The atomization cooling condition in the process is controlled so that the droplets are liquid, but undercooled or about to solidify when they contact the substrate surface. The droplets are essentially liquid and have not yet started to crystallize when they contact the metallic substrate surface. After impacting the substrate, the droplets form splats and continue to cool to temperatures well below their liquid temperature. Droplet sizes range generally from about 1 to 200 microns with the grain sizes in the deposition formed therefrom in the range of approximately 30-45 microns or greater.
None of the foregoing technologies however successfully fabricated a reactive spray atomization metal matrix composite with a low porosity. superplasticity, or a grain size generally lower than 10 microns, none successfully dealt with the inclusion of solid dispersoids into the atomized droplets, and none permitted controlled deposition products containing spatially varying physical and mechanical properties. Therefore, what is needed is an apparatus and methodology whereby such improved composites may be controllably and successfully fabricated at low cost and high reliability.